1. Field of the Invention
The present invention relates to a lens, and more particularly, to a Light Emitting Diode (LED) lens for radiating light from an LED chip in a predetermined beam angle to the outside and a backlight apparatus incorporating the same.
2. Description of the Related Art
A Liquid Crystal Display (LCD) is gaining attention as a next generation display according to the development of the electronic industry. The LCD is generally equipped with a backlight apparatus for illuminating an LCD panel from behind since the LCD panel does not light spontaneously.
FIG. 1 is a cross-sectional view illustrating a conventional LED which is proposed in U.S. Pat. No. 6,679,621 as a light source of a side emitting LCD backlight apparatus. Referring to FIG. 1, an LED 10 includes a plastic package 11 containing a heat conductive material therein, a pair of leads 12 for the input/output of electric signals, an LED chip 14 installed within the plastic package 11 and a lens 13 placed on the frame 11. The lens 13 functions to redirect light beams generated from the LED chip 14 to horizontal directions.
The lens 16 is optically designed so that the light beams, which are generated from the LED chip 14 and propagate in all directions, are refracted horizontally. While FIG. 1 illustrates the lens 13 having a generally mortar-shaped structure, the lens 13 may have more sophisticated structure according to angles of light emitted from the LED chip 14. There is a problem in that some of the light beams maybe uncontrollably directed in a vertical direction rather than being horizontally refracted.
In addition, when an LCD backlight apparatus is realized by using LEDs 10 as above, the LEDs 10 functioning as point light sources are mounted in line on PCBs of a predetermined length to form LED arrays 20 functioning as linear light sources as shown in FIG. 2. The LED arrays 20 are arranged in parallel with each other at a predetermined distance and reflectors 31 are attached to both sides of the LED arrays 20 to form a backlight apparatus 30, in which the reflectors 31 are designed to reflect light beams from the LED arrays 20 in vertical directions.
In the backlight apparatus 30 using the conventional LEDs as described above, since the light beams generated from the light sources or the LED chips 14 are refracted horizontally by the lens 13 and then reflected vertically by the reflectors 31, the light beams change their paths for several times. Therefore, the complicated paths cause light loss.
In addition, since the light beams emitted from the LED chips 14 spread for 360° about optical axes having vertical direction as shown in FIG. 1, their brightness reduces significantly in proportion to the distance from the light sources or the LED chips 14. Therefore, it is required to arrange the LED arrays 20 adjacent to each other in order to prevent brightness reduction.